The invention relates to inked ribbon cartridges, and particularly to cartridges for use on printers, such as shuttle matrix printers. Such cartridges are used for storing printing ribbon, such as inked fabric, carbon film, etc. within a storage chamber and from which chamber it may be withdrawn for printing. The invention also relates to a ribbon cartridge constructed to enable control of the position of the ribbon with respect to the print line to accommodate changes in ribbon drag produced during high dot density printing, to facilitate positioning of the cartridge in printing position, and to facilitate ribbon feed into the storage chamber without interference between the ribbon storage mechanism and the ribbon.
In high-speed shuttle matrix printer cartridges, for example of the type disclosed in parent application Ser. No. 081,245, ribbon is passed into the nip between a drive roller and driven roller enroute to a storage chamber. Strippers are used to play the ribbon emerging from the nip back and forth between opposite sides of the cartridge storage chamber to provide substantially uniform folds of ribbon throughout the extent of the storage chamber. The drive roller and driven roller also cause the ribbon to be removed from the storage chamber along an exit arm for disposition in a print position for coaction with a printhead having print wires or styli to produce a series of printing dots on the substrate. The ribbon is continuously moved by the drive and driven rollers through the print position and by way of an entrance arm back to the storage chamber.
One of the principal problems associated with printers of this type, particularly printers employing a high-speed shuttle matrix printer cartridge, is the capacity to accommodate the changes in ribbon drag caused by the interaction of the print wires and ribbon during high dot density printing when the print wires tend to brake or restrain ribbon movement. When the print wires or styli on the moving printhead impact the ribbon, they instantaneously brake the ribbon movement. As the print density, i.e., dots per inch, increases, this braking action may reach excessive proportions. With a relatively rigid entrance arm, and with the printhead moving in a direction opposite to the direction of movement of the ribbon, the braking or restraining action of the printhead on the ribbon causes the rotating drive wheels to increase the tension on the ribbon. This can cause the ribbon to skew out of alignment and, in an extreme case, cause the ribbon in contact with the print wires to be scraped, punctured or torn. Additionally, the stoppage of the ribbon caused by the interaction of the printhead with the ribbon results in the ribbon slipping on the drive wheel. This adversely affects the tracking of the ribbon into the cartridge, resulting in ribbon creasing, foldover, and twisting or causes the ribbon to be displaced in its own plane up or down the ribbon entrance arm. Twisting of the ribbon also causes the ribbon to track up or down relative to the line of print wires. This results in undesirable folding or wrinkling at the port of the entrance arm, and movement of the ribbon out of the wire printing range. This can lead to a derogation of print performance and ultimately to a failure of the printer to print at all.
When the ribbon is snagged or momentarily braked, and the printhead is moving in the direction of the ribbon flow, the printhead assists in advancing the ribbon more rapidly than the advance thereof caused by the drive wheels. This causes an excessive amount of ribbon to be pulled out of the ribbon cartridge and a slack in the ribbon between the printhead and the entrance nip of the drive rollers. This action causes similar results as stated above and may jam the ribbon in the cartridge.
It will be appreciated that the printhead moves rapidly back and forth along the print line. The adverse results caused by the interaction of the print wires and the ribbon and the back-and-forth movement of the printhead relative to the unidirectional movement of the ribbon quickly multiply. This results in improper ribbon flow, adversely affecting print quality, and causes damage to the ribbon and the print wires.
Accurate positioning and orientation of the cartridge in the printer is likewise essential for repeated quality printing. In solving the above-identified problems associated with the interaction of the printhead and the ribbon, it is essential that the cartridge at the same time be readily and easily mounted in the printer in proper position and orientation to address the banks of print wires to achieve effective quality printing.
Additionally, in those cartridges which employ a drive mechanism for folding ribbon into the storage chamber, there is the tendency, particularly as a result of the above-noted interaction between the printhead and ribbon, for the ribbon to track in the cartridge storage mechanism differently than in its designed track. Often, this locates the ribbon in the drive mechanism per se. Thus, the ribbon may become entangled in its own drive mechanism, causing a complete breakdown of the ribbon flow from the storage chamber into print position and return. It is therefore essential that the ribbon be maintained free and clear of the drive mechanism per se.